A Magnetoresistive Tunnel Junction (MTJ) is a device that changes its resistive state based on the state of magnetic materials within the device. An MTJ device includes a thin resistive layer between two ferromagnetic layers. One magnetic layer may be referred to as the reference layer. The other magnetic layer may be referred to as the free layer. The magnetic moment of the reference later generally maintains the same direction. Conversely, through application of a voltage across the junction, the direction of the magnetic moment of the free layer can be reversed. When the direction of the magnetic moment of both the free layer and the reference layer are the same, electrons can more easily tunnel through the thin resistive layer. In this state, the junction has a relatively low resistivity. Through application of a voltage with the opposite polarity, the magnetic moment of the free layer can be switched to oppose the direction of the magnetic moment of the reference layer. In this state, it is more difficult for electrons to tunnel through the resistive layer, causing the junction to have a relatively high resistivity. The different resistive states can be used to store logical values.
Improvements are desired in this field of endeavor. For example, the dipole interaction can be improved between the free and reference layers of the MTJ. Also, it is desired to reduce the density of the device.